The invention relates to a directly controlled magnetic valve which exhibits a great nominal diameter of the valve seat opening for connecting and shutting-off, respectively, two gas volumes, in particular, air volumes.
There are already known closed pre-controlled magnetic valve systems in which a pressure difference between the inlet of the valve and the outlet of the valve is utilized to operate a sealing means via a membrane or a piston. When the magnetic coil is de-energized, the input pressure is directed via a compensation bore into the space on top of the membrane to urge the same onto the valve seat. When the magnet opens the pre-controlled port, then the pressure on the membrane breaks down and the membrane will be raised by the input pressure applied, whereby the valve is opened in this way. This, however, requires a pressure difference between the two outlets of each valve system to allow valve actuation. From hydraulics technology there is further known to design the magnet armature in magnetic valves as pressure compensating slide valves. Moveable sealing systems are used for shutting-off the compensating slit, however, the shutting-off being in most cases not a complete one. Aside from the fact that, under cold conditions, there is the possibility of icing and sticking of the slide valve when very long slits have to be sealed, comparatively high breakaway forces and motion forces have to be applied to move the slide valve.
Furthermore, there has already been proposed to pre-control a differential piston by a magnetic valve. Thereby, the motive force is produced by a pressure applied to a control chamber or by the deairing of the control chamber. The moving sealings used are disadvantageous, since these require high breakaway forces, apart from not being sufficiently tight over their service life. When the pressure in the control chamber is relieved, the respective air is vented into the ambience which might lead to operational failures in the valve system. There has also been proposed a valve including a precontrolled membrane. In this case the motion is obtained by the pressure differences between two valve outlets in cooperation with a spring. In order to realize this proposal, the switching air with all its disadvantageous side-effects is required. Finally, in the also proposed use of seat valves very high spring forces and magnetic forces, respectively, are required, due to the high pressure forces applied for opening and closing the valves, the spring forces and magnetic forces very often cannot be realized in the interior space at disposal.
It is an object of the present invention to obviate the above mentioned disadvantages and to provide a magnetic valve of a great nominal diameter that requires a small constructional volume at a simultaneous low power requirement, and which further exhibits a minimum of leakage to the outside and between the two gas volumes when the valve is in the closed state, and which still further enables a fast compensation of pressure after the valve has been opened as well as a fast switching of the valve, irrespective of on which side of the valve the higher pressure is applied.
According to the invention the object is realized by the features of the first patent claim. A pressure compensation takes place due to a bore passing through the entire magnetic core and, hence, through the valve actuator and the valve tappet. Thus the same force is effective to the two leading faces of the valve actuator. Advantageously, the first and the second sealing means are of a same arrangement with respect to the geometrical longitudinal axis of the core. The sealing means, which correspond with each other, and which are arranged at the sealing disk and at the sealing seat as well as at the leading face of the valve actuator and at the face secured to the valve housing, whereby the face is adjacent to the leading face, have the same orientation to and a same distance from the geometrical longitudinal axis. In this way it is possible to compensate for tolerances in the valve actuator and in the valve tappet, respectively in the magnetic core and housing at a simultaneous operation of the two sealing means. When the tappet, which is of hollow cylindrical design and which is secured to the sealing disk, is pressed into the bore at the actuator, the pressing tool, while pressing, can be set- in step by step and simultaneously the flow rate can be measured until the ideal adjustment is obtained. It is, however, also possible to measure at first the actual value of the components and to compute the required pressure measure on the basis of these measured actual values. Thereby the pressure is so dimensioned that there will be no leakage over the entire length of pressure.
The sealing means, which correspond with each other, are provided either in the magnet of the valve, namely in the leading faces of the actuator and the magnet core, whereby these leading faces are adjacent to each other in facing opposition, or outside of the magnet at the other leading face of the actuator and at an adjacent preferably flanged face secured to the housing, wherein the face is of annular shape. The sealing means, which correspond with each other and which are arranged on faces facing each other, are, on the one hand, a sealing ring made of an elastomer which is disposed on or in the respective leading face and, on the other hand, an annular bulge or the like provided on the associated leading face. It is also possible that the elastomeric sealing rings are provided with bulges (to have them project out of their leading face), which then are urged onto the respective leading face, in this case the latter being designed flat. Anyhow, the sealing rings can be embedded fixedly and tightly in the corresponding leading faces, for example, by vulcanizing them into the latter. Advantageously, the embedding itself is, to balance for tolerances, resiliently designed by installation of additional spring means.
Advantageously, the sealing disk is provided with a tappet which projects into the bore of the valve actuator and preferably is pressfitted to the latter. The leading faces of the valve actuator and of the fixed core, whereby the faces are facing each other, can be designed plane or they can be provided with annular steps.
The directly controlled magnetic valve according to the present invention, which is used for switching over between two gas volumes, can be combined with a second magnetic valve for filling with or shutting-off a gaseous medium (air), the second magnetic valve being preferably also a directly controlled one. The shutting-off valve and the switching-over valve can be directly arranged at one block. Advantageously, the two valves are voltage-supplied via a common connector plug. In this case the filling and the discharge of the air volumes is carried out via the central compensation bores, which are substantially arranged about the geometrical axis of the core and of the valve actuator of the switching-over valve, whereby the compensation bores pass through all faces that are enclosed by the first and the second sealing means. In this way a complex boring will be avoided and space and material will be saved.
It is also possible to manufacture the armature (valve actuator), the tappet, and the sealing disk of the magnetic valve of the present invention in one piece. Alternatively, an additional advantageous embodiment will result, when the core is arranged between the armature and the sealing disk and the first and the second sealing means are provided on the respective leading faces on the side of the sealing disk. In this case the initially central bore can also laterally leave the tappet, provided that the remaining parts of the magnetic valve are correspondingly designed and arranged.
According to the present invention the valve can be so designed that, when the electromagnet is de-energized, it can be opened (currentless open) or closed (currentless closed). Particularly advantageous according to the present invention is the solution with the currentless open magnetic valves, since there is, due to the pressure compensation, only a low spring force necessary to release the armature and, consequently, for lifting the sealing disk from its seat. Likewise, only a comparatively low energy is required for shutting-off and keeping the magnetic valve shut, due to the low spring force.